X-ray Photoelectron Spectrum of Co Implanted into Sapphire

Abstract

Co ions were implanted into colorless and transparent synthetic sapphires with doses of 5X10¹⁶-5X10¹⁷ ions/cm² at an energy of 20 keV. Optical transparencies in the visible region (400-700nm) and XPS (X-ray photoelectron spectroscopy) spectrum were measured for as-implanted samples and annealed ones up to 1200°C in sequence. Although an as-implanted sample showed only dark grey, on heating the sample its color tone was gradually changed. The color turned green when it was heated at 800°C for 3 h and showed large absorption in the range of wavelength shoter than about 530 nm and a small dip in the range of 600-660 nm. Light blue color was obtained by heating the sample at 1000°C for 3 h and showed a broad absorption peak centered at about 610 nm.
XPS spectra of Co2p_3/2 implanted into sapphire was changed when it was heated at 800 or 1000°C. Although the spectra for the as-implanted sample almost coincided with that of metal, the spectrum for the annealed ones showed two peaks, one near the metallic state and the other apart by about 3 eV in the binding energy, which indicates the existence of two types of electronic configurations of Co with different binding energies in the colored sapphire.